1. Field of the Invention
This invention relates to paint and varnish remover compositions, and more particularly, to a method of activating NMP and/or BLO for more effective paint and varnish removing action, and to compositions thereof.
2. Description of the Prior Art
The term "varnish and paint remover" as applied herein refers to chemical compositions which can strip or facilitate stripping of coatings, such as, paint, varnish, lacquer, shellac, polyurethane finishes and enamels, used to protect substrates such as wood and metal and to beautify them.
Methylene chloride paint strippers are currently the industry standard for stripper performance. Methylene chloride strippers are effective for quickly softening most types of paints. The speed at which methylene chloride performs is believed to be due to its high solvent power coupled with high volatility as reflected by its extremely fast evaporation rate. This high volatility shortens the work life of methylene chloride paint strippers. Frequently, when methylene chloride paint strippers are used on thick accumulations of paint, more than one application is required since the work life is insufficient to permit penetration through the accumulation of paint.
Methylene chloride is a chlorinated solvent which is closely regulated for environmental protection Recently, it was discovered that methylene chloride can cause tumors in rats and mice Since that discovery, the wide use of that solvent by industry and consumers has come under close scrutiny by federal regulatory agencies.
N-methyl-2-pyrrolidone (NMP) has been employed in place of methylene chloride as the active ingredient in paint stripper compositions. Nelson, in U.S. Pat. No. 4,759,510, for example, described a composition for this use having low volatility which included about 20% to 90% by weight of NMP and 30% to 70% by weight of an aromatic hydrocarbon solvent.
Mixtures of NMP and .gamma.-butyrolactone (BLO) also have been used as liquid formulations for removing screen printing inks. Madsen, in U.S. Pat. No. 4,836,950, for example, described such a liquid composition which included 1-25% by volume of NMP and/or BLO. Valasek, similarly, in U.S. Pat. No. 4,664,721, described a composition which included 30-85% by weight of NMP and 10-35% by weight of an oxygenated solvent selected from esters and ethers. BLO was mentioned as a suitable ether, although butoxyethanol and cyclohexanone were preferred. Caster, in U.S. Pat. No. 4,865,758 described a method of removing paint with a lower alkyl substituted 2-oxazolidinone. In comparative results reported therein, it was disclosed that ethyl 3-ethoxypropionate had no effect on paint removal. McCullins, in British 1,487,737, described a paint remover composition for aerosol type paints in the form of a gel which included methyl ethyl ketone, ethyl acetae, ethoxyethanol and 2-ethoxyethyl acetate. This mixture of solvents was considered effective for paint sprayed graffiti as a viscous, transparent gel containing particles of silica or alumina in suspension. Palmer, in U.S. Pat. No. 4,120,810, described paint remover compositions of NMP and/or BLO, and at least 35 mole % of blends of alkyl naphthalenes and alkyl benzenes.
These and other compositions, however, have not proven particularly effective for removing paint and varnish from wood and metal surfaces, without containing objectionable halogenated or aromatic compounds. Furthermore, they do not possess the attributes of being biodegradable, non-flammable, having a low vapor pressure and low toxicity.
Accordingly, it is the object of the present invention to satisfy the above criteria for an environmentally safe commercial product for removing paint and varnish from surfaces, and to perform such removal effectively with less material than other related products on the market today.
These and other objects and features of the invention will be made apparent from the following description of the invention